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Investments in Unconsolidated Entities (Details) - USD ($) $ in Millions | Sep. 30, 2018 | Dec. 31, 2017
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White Mountains |  |
Investments in unconsolidated affiliates |  |
Total other long-term investments | $ 289.7 | $ 208.8
Equity method eligible private equity securities, at fair value |  |
Investments in unconsolidated affiliates |  |
Total other long-term investments | 126.4 | 83.2
Equity method eligible private equity securities, at fair value | White Mountains |  |
Investments in unconsolidated affiliates |  |
Total other long-term investments | 97.3 | 58.0
Investments, accounted for under the equity method | White Mountains |  |
Investments in unconsolidated affiliates |  |
Total other long-term investments | 11.6 | 4.6
Total investments in equity method eligible unconsolidated entities | White Mountains |  |
Investments in unconsolidated affiliates |  |
Total other long-term investments | 108.9 | 62.6
Other unconsolidated investments | White Mountains |  |
Investments in unconsolidated affiliates |  |
Total other long-term investments | $ 180.8 | $ 146.2

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- Details
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